Bed height and material density effects on fluidized bed hydrodynamics

Escudero, David R.; Heindel, Theodore J.

doi:10.1016/j.ces.2011.04.036

Cited by 87 publications

(28 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition Figure 5 show that the general fluidization behaviour was similar for glass beads and copper particles, with a region of higher gas holdup in the center, and a region of low gas holdup (higher solids concentration) near the walls. Similar results were revealed by Franka et al 15 for two different 3D beds and Escudero et al 16…”

Section: B Effects Of Particle Density On Time-averaged Solids Holdusupporting

confidence: 89%

Untitled

2016

IPCSE

View full text Add to dashboard Cite

The main goal of this study is to further understand the fluidized bed hydrodynamics by determining the effects of superficial gas velocity and bed density on the hydrodynamics of gas-solid fluidized beds by using a 14-cm-diameter Plexiglas cylindrical fluidized bed column, air at room temperature was used as the fluidizing gas, two different Geld art type-B particles were used glass bead and copper particle with material densities of 2500, 5300 Kg/m 3 respectively with the same size particle 210 µm. Three different superficial gas velocities were investigated U g =25, 30, and 35 cm/s. Non-invasive flow measurement technique gamma ray computed tomography (CT) has been used to measure the timeaveraged cross-sectional and radial profiles of solids and gas holdups distribution. The results show that local time-averaged gas holdup is a function of bed material density, that as material density decreases, gas holdup increases, gas holdup increases with increasing superficial gas velocities.Keywords: fluidized beds hydrodynamics, computed tomography, gas hold-up In this study the effects of gas velocity and material density on local time-averaged gas holdup in fluidized bed are investigated by using gamma ray computed tomography technique (CT). Therefore, our detailed local measurements of the cross-sectional distribution and radial pro-files of solids and gas holdups will be valuable benchmarking data to evaluate and validate these CFD. Experimental setupThe experimental works were carried out in 14 cm cold flow fluidized bed. A schematic diagram of the setup used in this study is illustrated in Figure 1. The 14 cm column was 1.68 m high connected from the top with an upper section that had a diameter of 42 cm and was 84 cm high; this upper section of the fluidized bed (the disengagement zone) had a larger diameter to reduce the superficial gas velocity of the gas phase to enhance the solids separation. The plenum was located at the bottom, which consisted of a sparger tube. The gas phase at ambient temperature was introduced through a distributor at the bottom after passing through the sparger. The gas distributor was made of a porous polyethylene sheet and had a pore size of 40 µm. The sparger was plugged at one end, and had 14 holes, all facing downward with respect to the column. The properties of solids, static bed height used in the experiments are listed in Table 1. Measurement technique a. Dual Source gamma ray computed tomography (DSCT)DSCT consists of two sealed sources (Cs-137 and Co-60) and two sets of 15 NaI detectors located in front on each sealed source as shown in Figure 2. In this work CT experiments were performed under two-phase conditions gas and solids, and hence a single sealed source (Cs-137) and its related 15 NaI scintillation detectors located opposite to the (Cs-137) sealed source has been used. As shown in Figure 2 the sources and detectors are built on a rotary plate to move together in 360˚ around the studied bed providing 197 views in each scan and 21 projections in each view...

show abstract

Section: B Effects Of Particle Density On Time-averaged Solids Holdusupporting

confidence: 89%

Untitled

2016

IPCSE

View full text Add to dashboard Cite

show abstract

“…X-ray visualization has proven to be a useful and relatively inexpensive tool in providing good qualitative and quantitative data of dynamic behavior [16]. Successful measurements of time-average gas holdup have been made using these techniques [13,[17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Comparisons of Annular Hydrodynamic Structures in 3D Fluidized Beds Using X-Ray Computed Tomography Imaging

Drake

Heindel

2012

Journal of Fluids Engineering

Self Cite

View full text Add to dashboard Cite

Fluidized beds are common equipment in many process industries. Knowledge of the hydrodynamics within a fluidized bed on the local scale is important for the improvement of scale-up and process efficiencies. This knowledge is lacking due to limited observational technologies at the local scale. This paper uses X-ray computed tomography (CT) imaging to describe the local time-average gas holdup differences of annular hydrodynamic structures that arise through axisymmetric annular flow in a 10.2 cm and 15.2 cm diameter cold flow fluidized bed. The aeration scheme used is similar to that provided by a porous plate and hydrodynamic results can be directly compared. Geldart type B glass bead, ground walnut shell, and crushed corncob particles were studied at various superficial gas velocities. Assuming axisymmetry, the local 3D timeaverage gas holdup data acquired through X-ray CT imaging was averaged over concentric annuli, resulting in a 2D annular and time-average gas holdup map. These gas holdup maps show that four different types of annular hydrodynamic structures occur in the fluidized beds of this study: zones of (1) aeration jetting, (2) bubble coalescence, (3) bubble rise, and (4) particle shear. Changes in the superficial gas velocities, bed diameters, and bed material densities display changes in these zones. The 2D gas holdup maps provide a benchmark that can be used by computational fluid dynamic (CFD) users for the direct comparisons of 2D models, assuming axisymmetric annular flow.Keywords annular flow, fluidized bed, gas holdup, hydrodynamic structure, X-ray computed tomography Fluidized beds are common equipment in many process industries. Knowledge of the hydrodynamics within a fluidized bed on the local scale is important for the improvement of scale-up and process efficiencies. This knowledge is lacking due to limited observational technologies at the local scale. This paper uses X-ray computed tomography (CT) imaging to describe the local time-average gas holdup differences of annular hydrodynamic structures that arise through axisymmetric annular flow in a 10.2 cm and 15.2 cm diameter cold flow fluidized bed. The aeration scheme used is similar to that provided by a porous plate and hydrodynamic results can be directly compared. Geldart type B glass bead, ground walnut shell, and crushed corncob particles were studied at various superficial gas velocities. Assuming axisymmetry, the local 3D time-average gas holdup data acquired through X-ray CT imaging was averaged over concentric annuli, resulting in a 2D annular and time-average gas holdup map. These gas holdup maps show that four different types of annular hydrodynamic structures occur in the fluidized beds of this study: zones of (1) aeration jetting, (2) bubble coalescence, (3) bubble rise, and (4) particle shear. Changes in the superficial gas velocities, bed diameters, and bed material densities display changes in these zones. The 2D gas holdup maps provide a benchmark that can be used by computational fluid dynamic (CFD) users fo...

show abstract

“…Application of a visualisation method for distribution of the solid phase can contribute to optimise the design of reactors, parameters of their operation, as well as lead to improved knowledge of the fluidisation phenomenon. Hydrodynamics of the fluidised bed has been widely presented in the literature (Basu, 2006;Escudero and Heindel, 2011;Yang et al 2007).…”

Section: Current Applications Of Ect Tomography For Research On Fluidmentioning

confidence: 99%

“…Much attention is given to methods of determination of local velocity (Doppler laser anemometry), bubble formation and the most important in fluidised beds: solid concentration (X-ray and gamma-ray tomography, capacitance tomography) (Wiesendorf and Werther, 2000). Tomographic methods were also used in measurements of bed height as well as determination of the minimum fluidisation velocity (Escudero and Heindel, 2011).…”

Section: Introductionmentioning

confidence: 99%

Applications of Electrical Capacitance Tomography for Research on Phenomena Occurring in the Fluidised Bed Reactors

Porzuczek¹

2014

Chemical and Process Engineering

View full text Add to dashboard Cite

The paper presents a review of current achievements in the Electrical Capacitance Tomography (ECT) in relation to its possible applications in the study of phenomena occurring in fluidised bed reactors. Reactors of that kind are being increasingly used in chemical engineering, energetics (fluidised bed boilers) or industrial dryers. However, not all phenomena in the fluidised bed have been thoroughly understood. This results in the need to explore and develop new research methods. Various aspects of ECT operation and data processing are described with their applicability in scientific research. The idea for investigation of temperature distribution in the fluidised bed, using multimodal tomography, is also introduced. Metrological requirements of process tomography such as sensitivity, resolution, and speed of data acquiring are noted.

show abstract

Bed height and material density effects on fluidized bed hydrodynamics

Cited by 87 publications

References 32 publications

Untitled

Untitled

Comparisons of Annular Hydrodynamic Structures in 3D Fluidized Beds Using X-Ray Computed Tomography Imaging

Applications of Electrical Capacitance Tomography for Research on Phenomena Occurring in the Fluidised Bed Reactors

Contact Info

Product

Resources

About